Method for decomposing aliphatic polycarbonate resin

Abstract

The present invention provides a method for efficiently decomposing aliphatic polycarbonate resins and / or compositions containing said aliphatic polycarbonate resins. [Solution] A method for decomposing a polycarbonate resin and / or a composition containing the polycarbonate resin, comprising a decomposition step of decomposing the polycarbonate resin and / or the composition in the presence of water, one or more organic solvents and one or more alkali metal salts, wherein the polycarbonate resin is a resin having structural units derived from aliphatic alcohols having two or more hydroxyl groups and carbonate bonds, and in the decomposition step, the polycarbonate resin and / or the composition is added in two or more portions, and the step of adding the polycarbonate resin and / or the composition a second time is performed after at least a portion of the polycarbonate resin and / or the composition added the first time has dissolved.

Description

Technical Field

[0001] The present invention relates to a method for decomposing an aliphatic polycarbonate resin and / or a composition containing the polycarbonate resin.

Background Art

[0002] Plastics are lightweight, durable, and inexpensive, and are thus mass-produced not only in Japan but also around the world. Since many of these plastics are used as "disposable" items, some are not properly processed and end up flowing into the environment. Specifically, plastic waste flows from rivers into the sea, where it degrades due to waves and ultraviolet rays and becomes less than 5 mm in size. Such small plastic waste is called microplastics. Animals and fish may accidentally ingest this microplastic. Thus, plastic waste has a significant impact on the ecosystem and has recently been regarded as a global problem known as the marine plastic problem. Polycarbonate resins are used in a wide range of fields due to their transparency, mechanical properties, flame retardancy, dimensional stability, and electrical properties, and this polycarbonate resin is no exception.

[0003] As one method of recycling polycarbonate resins, there is chemical recycling in which polycarbonate resins are chemically decomposed back to monomers for reuse. For example, methods of chemical recycling using hydrolysis or alcoholysis are known (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the demand for recycling aliphatic polycarbonate resins has been increasing, and there is a need for efficient methods to decompose aliphatic polycarbonate resins.

[0006] The present invention has been made in view of these circumstances and aims to provide a method for efficiently decomposing aliphatic polycarbonate resin and / or a composition containing said aliphatic polycarbonate resin. [Means for solving the problem]

[0007] The inventors of this invention conducted diligent research to solve the above problems and found that the above problems could be solved by decomposing the resin using a specific method, thus completing the present invention. In other words, the present invention includes the following embodiments, and also includes embodiments that combine the features of each of the following embodiments.

[0008] <1> A method for decomposing a polycarbonate resin and / or a composition containing said polycarbonate resin, The process includes a decomposition step of decomposing the polycarbonate resin and / or the composition in the presence of water, one or more organic solvents and one or more alkali metal salts, The polycarbonate resin is a resin having structural units derived from aliphatic alcohols having two or more hydroxyl groups and carbonate bonds. A method for decomposing a polycarbonate resin and / or a composition containing the polycarbonate resin, wherein in the decomposition step, the polycarbonate resin and / or the composition is added in two or more portions, and the step of adding the polycarbonate resin and / or the composition a second time is performed after at least a portion of the polycarbonate resin and / or the composition added the first time has dissolved. <2> The decomposition step includes adding the polycarbonate resin and / or the composition to a mixture containing the water, the organic solvent, and the alkali metal salt, which has been adjusted to a temperature of 50°C to 200°C. <1> Methods used. <3> The one or more organic solvents include polar organic solvents. <1> or <2> Methods used. <4> The one or more alkali metal salts include a metal hydroxide, <1> from <3> One of the methods described above. <5> The amount of water is 6.0 moles or more and 100 moles or less per 1.0 mole of repeating units of the polycarbonate resin in the composition, <1> from <4> One of the methods described above. <6> The amount of the one or more alkali metal salts is 0.6 moles or more and 20 moles or less per 1.0 mole of repeating units of the polycarbonate resin in the polycarbonate resin and / or the composition, <1> from <5> One of the methods described above. <7> The process includes a decomposition step of decomposing the polycarbonate resin and / or the composition to obtain decomposition products, a neutralization step of adding acid after the decomposition step to neutralize it, and a filtration step of removing solid foreign matter after the neutralization step. <1> from <6> One of the methods described above. <8> Furthermore, the process includes a removal step of removing the organic solvent and water by vacuum distillation, and a monomer recovery step of distilling the solids generated in the vacuum distillation of the removal step under high vacuum to obtain the monomer, which is an aliphatic alcohol having two or more hydroxyl groups. <1> from <7> One of the methods described above. <9> Furthermore, the process includes a removal step of removing the organic solvent and water by vacuum distillation, a step of removing insoluble matter by dissolving the solids generated in the vacuum distillation step in alcohol and filtering it, and a step of crystallizing and recovering the aliphatic alcohol having two or more hydroxyl groups, which is the monomer. <1> from <7> One of the methods described above. <10> The obtained aliphatic alcohol is further purified by one or more of the following steps: crystallization, filtration, and distillation. <8> or <9> Methods used. <11> The aliphatic alcohol containing two or more hydroxyl groups includes an aliphatic alcohol represented by the following formula (1m), <1> from <10> One of the methods described above. [ka] <12> The polycarbonate resin contains structural units derived from a dihydroxy compound different from the dihydroxy compound represented by formula (1m), <11> Methods used. <13> The aliphatic alcohol containing two or more hydroxyl groups includes 1,4-cyclohexanedimethanol. <1> from <12> One of the methods described above. <13> The aforementioned <1> from <13> A method for producing monomers constituting the polycarbonate resin, comprising any of the following methods. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for efficiently decomposing aliphatic polycarbonate resin and / or a composition containing said aliphatic polycarbonate resin. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is just one example of how the present invention can be carried out, and the present invention is not limited to the following description as long as it does not exceed the gist of the invention. In this specification, when the expression "~" is used, it is used to mean an expression that includes the numerical value or physical property value before and after it.

[0011] <Disassembly method> The present invention relates to a method for decomposing a polycarbonate resin and / or a composition containing the polycarbonate resin, comprising a decomposition step of decomposing the polycarbonate resin and / or the composition in the presence of water, one or more organic solvents and one or more alkali metal salts, wherein the polycarbonate resin is a resin having structural units derived from aliphatic alcohols having two or more hydroxyl groups and carbonate bonds, and in the decomposition step, the polycarbonate resin and / or the composition is added in two or more portions, and the step of adding the polycarbonate resin and / or the composition a second time is performed after at least a portion of the polycarbonate resin and / or the composition added the first time has dissolved, and the method for decomposing a polycarbonate resin and / or a composition containing the polycarbonate resin (hereinafter sometimes referred to as "the decomposition method of the present invention").

[0012] Hereinafter, "a resin having structural units derived from aliphatic alcohols having two or more hydroxyl groups and carbonate bonds" will be referred to as "aliphatic polycarbonate resin," and "aliphatic polycarbonate resin" and "compositions containing aliphatic polycarbonate resin" will be collectively referred to as "aliphatic polycarbonate resins."

[0013] Aliphatic polycarbonate resins have lower solubility in organic solvents and a relatively slower hydrolysis reaction rate compared to general aromatic polycarbonate resins. However, by following the procedure of the above embodiment, the amount of undissolved resin present in the reaction system can be minimized compared to a method in which the entire amount of aliphatic polycarbonate resins used is added at once. This can be expected to reduce fusion between resins and the load on the stirrer, or improve the overall dispersibility or fluidity of the reaction system.

[0014] (Aliphatic polycarbonate resins) The aliphatic polycarbonate resins used in the decomposition method of the present invention are aliphatic polycarbonate resins and / or compositions containing aliphatic polycarbonate resins. The aliphatic polycarbonate resin is a polymer containing structural units derived from an aliphatic alcohol having two or more hydroxy groups and carbonate bonds (-O-C(=O)-O-). When the aliphatic alcohol having two or more hydroxy groups is represented as HO-X-OH, the aliphatic polycarbonate resin contains repeating units represented by [-O-X-O-C(=O)-].

[0015] Examples of the aliphatic alcohol having two or more hydroxy groups include isosorbide, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, pentacyclopentadecane dimethanol, adamantane dimethanol, biscyclohexane diol, and the like.

[0016] Preferable aliphatic polycarbonate resins include aliphatic polycarbonate resins containing repeating units represented by the following general formula (1p).

[0017]

Chemical formula

[0018] The repeating unit represented by the general formula (1p) is a repeating unit composed of a structural unit derived from a dihydroxy compound represented by the following general formula (1m) and -C(=O)-.

[0019]

Chemical formula

[0020] Other preferable aliphatic polycarbonate resins include aliphatic polycarbonate resins containing repeating units represented by the following general formula (2p). The repeating unit represented by the following general formula (2p) is a repeating unit composed of a structural unit derived from 1,4-cyclohexanedimethanol and -C(=O)-.

[0021] [ka]

[0022] Other suitable aliphatic polycarbonate resins include those containing repeating units represented by the following formula (3p). The repeating units represented by the following general formula (3p) consist of structural units derived from 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane and repeating units consisting of -C(=O)-.

[0023] [ka]

[0024] Furthermore, the aliphatic polycarbonate resin is not limited to polycarbonate homopolymers, but may also be a polycarbonate copolymer. An example of a copolymer is a polycarbonate copolymer comprising a repeating unit represented by the general formula (1p) and one or more repeating units that include constituent units derived from a dihydroxy compound different from the dihydroxy compound represented by the general formula (1m). Examples of dihydroxy compounds different from the dihydroxy compound represented by the general formula (1m) include aliphatic alcohols containing two or more hydroxyl groups that are different from the dihydroxy compound represented by the general formula (1m), and specifically, alicyclic dihydroxy compounds other than the dihydroxy compound represented by the general formula (1m) are included.

[0025] Among them, one suitable copolymer is a polycarbonate copolymer comprising a repeating unit (A-1) represented by the general formula (1p) and a repeating unit (A-2) containing constituent units derived from an alicyclic dihydroxy compound, wherein when the total of repeating units (A-1) and (A-2) is 100 mol%, the ratio of repeating units (A-1):repeating units (A-2) is 1:99 to 99:1 (mol%), and the alicyclic dihydroxy compound is 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, adamantanedimethanol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane or biscyclohexanediol, and the Abbe number is 50 or higher.

[0026] Furthermore, the polycarbonate copolymer only needs to be primarily composed of the repeating units represented by [-OXOC(=O)-], and may have multiple repeating units represented by [-OXOC(=O)-], or it may contain repeating units represented by [-OXOC(=O)-] and other repeating units other than [-OXOC(=O)-]. As for the form of the copolymer, random copolymers, alternating copolymers, block copolymers, graft copolymers, etc., can be used. The proportion of other repeating units in the polycarbonate copolymer is usually less than 90 mol%, preferably 75 mol% or less, preferably 5 mol% or more, and more preferably 25 mol% or more.

[0027] Furthermore, the aliphatic polycarbonate resin may consist of one type of aliphatic polycarbonate resin, or it may be a blend of two or more types of aliphatic polycarbonate resins.

[0028] A composition containing an aliphatic polycarbonate resin contains, in addition to the aliphatic polycarbonate resin, other resins (other resins) and various additives. Examples of compositions containing resins other than aliphatic polycarbonate resin include alloys of aliphatic polycarbonate and polyester, alloys of aliphatic polycarbonate and polyarylate, and alloys of aliphatic polycarbonate and polycarbonates other than aliphatic polycarbonate. When using a composition containing resins other than aliphatic polycarbonate resin, for example, a composition containing 10% by mass or more of aliphatic polycarbonate resin can be used.

[0029] Furthermore, aliphatic polycarbonate resins can be used by mixing two or more different aliphatic polycarbonate resins. Two or more types of aliphatic polycarbonate resins may be used, two or more compositions containing aliphatic polycarbonate resins may be used, or one or more types of aliphatic polycarbonate resins and one or more compositions containing aliphatic polycarbonate resins may be used in combination.

[0030] In one embodiment, the aliphatic polycarbonate resins used in the decomposition method of the present invention can be aliphatic polycarbonate resins contained in waste plastics, which is preferable in that it makes effective use of resources.

[0031] Waste plastics can be used after being washed, crushed, or pulverized as appropriate. Methods of crushing waste plastics include coarse crushing using a jaw crusher or rotary crusher to break them down to 20 cm or less, medium crushing using a rotary crusher, cone crusher, or mill to break them down to 1 cm or less, and pulverization using a mill to break them down to 1 mm or less. The goal is simply to break them down to a size that can be supplied to the decomposition tank. In the case of thin plastics such as CDs and DVDs, they can be shredded using a shredder or similar device before being supplied to the decomposition tank. It is also possible to remove beforehand any parts formed by components other than polycarbonate resin, such as other resins in copolymers or blends, or the layers on the surface or back of optical discs.

[0032] (water) In the decomposition method of the present invention, the resin is decomposed by hydrolysis, and therefore the decomposition reaction proceeds in the presence of water. The amount of water used is preferably 1.0 or higher, more preferably 3.0 or higher, even more preferably 6.0 or higher, and particularly preferably 10.0 or higher, and also preferably 200.0 or lower, more preferably 150.0 or lower, even more preferably 100.0 or lower, and may also be 80.0 or lower or 50.0 or lower. When the amount of water used is above the lower limit, the base, which acts as a catalyst, dissolves easily, and improvements in catalytic effect, decomposition rate, or yield can be expected. When the amount of water used is below the upper limit, the volume can be reduced, and improvements in manufacturing efficiency can be expected.

[0033] The molecular weight of the repeating units in aliphatic polycarbonate resins can be calculated from 1H-NMR, for example, as described later in the examples. When the aliphatic polycarbonate resin is a copolymer, the average molecular weight of the repeating units is used as the molecular weight of the repeating units. For example, if the repeating unit consists of repeating unit (I) and repeating unit (II), then (molecular weight of the repeating unit) = (ratio of repeating unit (I) when repeating unit (II) is set to 100 mol%) × (molecular weight of repeating unit (I)) + (ratio of repeating unit (II) when repeating unit (I) is set to 100 mol%) × (molecular weight of repeating unit (II)).

[0034] (organic solvent) The decomposition method of the present invention is carried out in the presence of an organic solvent.

[0035] The organic solvent should preferably have an affinity for alkali metal salts, as this facilitates the decomposition reaction of the resin. The amount of organic solvent used is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, even more preferably 3.0 parts by mass or more, and preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, and even more preferably 10.0 parts by mass or less, per 1.0 part by mass of aliphatic polycarbonate resin. Using an amount of organic solvent above the lower limit of the above limits results in good dispersion of the aliphatic polycarbonate resin, which facilitates the decomposition reaction or shortens the decomposition time, thus tending to improve efficiency. Using an amount below the upper limit of the above limits allows for a smaller volume to be used, thus tending to improve manufacturing efficiency.

[0036] The organic solvent may be a nonpolar solvent such as toluene or xylene, but it is preferable to include a polar organic solvent that readily dissolves the aliphatic alcohols produced by decomposition. Using a polar organic solvent improves dispersibility because the decomposition products do not separate and form a solution, and because it has good affinity with alkali metal aqueous solutions, thus enabling more effective decomposition of the resin. The content of the polar organic solvent in the organic solvent is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more. As the polar organic solvent, aliphatic alcohols, aromatic alcohols, cyclic or chain hydrocarbons containing heteroatoms, etc., can be used.

[0037] [Aliphatic monoalcohols] Examples of aliphatic monoalcohols include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol, n-pentanol, i-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, and n-dodecanol. Among these, the aliphatic monoalcohol is preferably an alcohol having 1 to 5 carbon atoms, and more preferably one selected from the group consisting of methanol, ethanol, i-propanol, and n-butanol.

[0038] [Aromatic monoalcohols] Aromatic monoalcohols are compounds in which one hydroxyl group is bonded to a carbon atom that forms an aromatic ring, and preferably one or more selected from the group consisting of phenol, cresol, and xylenol are used.

[0039] Examples of cresol include ortho-cresol, meta-cresol, para-cresol, and mixtures of isomers containing one or more of these. Preferably, since liquids at around 30°C are easy to supply to the decomposition vessel, ortho-cresol, meta-cresol, a mixture of isomers of meta-cresol and para-cresol, or a mixture of isomers of ortho-cresol, meta-cresol, and para-cresol are used.

[0040] Examples of xylenol include 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,5-xylenol, 3,4-xylenol, and mixtures of isomers containing one or more of these. 2,5-xylenol is preferred because it is readily available industrially at low cost.

[0041] [Hyperheteronite-containing hydrocarbons] In this specification, heteroatom-containing hydrocarbons mean compounds in which some of the carbon atoms in the hydrocarbon skeleton are replaced by heteroatoms. When heteroatom-containing hydrocarbons are used as polar organic solvents, the hydrocarbon skeleton before substitution with heteroatoms may be a skeleton with 3 to 20 carbon atoms, and the compound may be one in which n carbon atoms in the skeleton are replaced by heteroatoms, in which case the number of carbon atoms in the hydrocarbon skeleton replaced by heteroatoms is mn. Furthermore, the carbon skeleton can have a chain-like or cyclic structure, and preferably one with a cyclic structure. The aforementioned m is preferably 4 or more, more preferably 15 or less, more preferably 12 or less, even more preferably 10 or less, particularly preferably 8 or less, and most preferably 7 or less. Having m above the lower limit allows the boiling point to be above a certain temperature, preventing excessive volatilization under reaction conditions. Furthermore, having m below the upper limit allows it to have a melting point where it becomes a liquid at the reaction temperature, making it suitable for use as a solvent. The hydrocarbon skeleton may have branched chains, substituents, or unsaturated bonds. As the heteroatom, you can use O (oxygen), S (sulfur), N (nitrogen), P (phosphorus), etc., but preferably one or more of O (oxygen) and N (nitrogen), and from the viewpoint of suppressing reactivity with aliphatic polycarbonate resins and the resulting decomposition products, O (oxygen) is more preferable.

[0042] Examples of heteroatom-containing hydrocarbons include 4-methyltetrapyran and tetrahydrofuran.

[0043] In particular, preferred organic solvents include phenol, tetrahydrofuran, 4-methyltetrapyran, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol, n-pentanol, i-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, and n-dodecanol. These organic solvents can be used individually or in combination of two or more.

[0044] (catalyst) One of the features of the decomposition method of the present invention is the use of an alkali metal salt as a catalyst. Preferably, the alkali metal salt includes an alkali metal hydroxide.

[0045] [Alkali metal hydroxides] Alkali metal hydroxides are salts of alkali metal ions (M+) and hydroxide ions (OH-), and are compounds represented as MOH (where M represents an alkali metal atom). Sodium hydroxide or potassium hydroxide are preferred as alkali metal hydroxides.

[0046] The molar ratio of alkali metal salt to repeating units of aliphatic polycarbonate resin in aliphatic polycarbonate resins ((mass of alkali metal salt used [g] / molecular weight of alkali metal salt [g / mol]) / (mass of aliphatic polycarbonate resins used [g] / molecular weight of repeating units [g / mol])) is preferably 0.6 or higher, more preferably 1.0 or higher, preferably 20.0 or lower, more preferably 10.0 or lower, and even more preferably 5.0 or lower. When the molar ratio is above the lower limit, an improvement in the decomposition rate of the resin and an improvement in efficiency by shortening the decomposition time can be expected. Furthermore, when the molar ratio is below the upper limit, the decomposition of decomposition products such as monomers obtained can be suppressed, and the amount of acid required for neutralization after decomposition can be suppressed, which tends to improve manufacturing efficiency.

[0047] Furthermore, in one embodiment of the decomposition method of the present invention, a phase transfer catalyst may be used. A phase transfer catalyst is generally a molecule or salt having hydrophilic and hydrophobic parts, and has the effect of promoting the movement of hydrophilic substances (including ions) to a nonpolar solvent, or the movement of hydrophobic substances (including ions) to a polar solvent. By using a phase transfer catalyst in a two-phase chemical reaction, the aforementioned effect promotes the movement of substances before and after the reaction, and it is expected that this will promote the reaction between substances that are separated into different phases and do not easily come into contact, such as the reaction between hydrophobic organic molecules such as resins and hydrophilic bases.

[0048] The aliphatic polycarbonate resins used in this invention are usually insoluble in water. However, since this invention hydrolyzes the aliphatic polycarbonate resins with an alkali metal salt, which is a base catalyst, it is necessary for the aliphatic polycarbonate resins and any oligomers that may be generated during decomposition to come into contact with the alkali metal salt and water. Therefore, by using a phase transfer catalyst in the reaction, it is expected that contact between the aliphatic polycarbonate resins and oligomers and the alkali metal salt and water will be promoted, thereby accelerating the reaction.

[0049] The type of phase transfer catalyst is not particularly limited, and known and commercially available catalysts can be used, such as sulfonium salts, phosphonium salts, quaternary ammonium salts, and crown ethers. In the examples described later, tetrabutylammonium bromide (TBAB) was used as an example, but this embodiment is not limited to this.

[0050] (decomposition products) The present invention relates to a decomposition method for aliphatic polycarbonate resins, which involves decomposition (i.e., depolymerization) to obtain decomposition products. The decomposition products are monomers and oligomers that constitute the aliphatic polycarbonate resins. Preferably, the decomposition products include monomers.

[0051] (Monomers that make up aliphatic polycarbonate resin) The decomposition products obtained by the decomposition method of the present invention include monomers corresponding to the structure of structural units derived from aliphatic alcohols having two or more hydroxyl groups in the aliphatic polycarbonate resin, i.e., aliphatic alcohols having two or more hydroxyl groups. For example, a dihydroxy compound represented by general formula (1m) can be obtained from the repeating unit represented by general formula (1p). A polycarbonate resin copolymer containing the repeating unit represented by general formula (1p) and the repeating unit represented by general formula (2p) can be obtained from a dihydroxy compound represented by general formula (1m) and 1,4-cyclohexanedimethanol.

[0052] (decomposition process) The decomposition method of the present invention comprises a decomposition step of decomposing aliphatic polycarbonate resins to obtain decomposition products, wherein the aliphatic polycarbonate resins are added in two or more separate steps. In other words, the decomposition step includes the following (a) and (b).

[0053] (a) Mixing water, one or more organic solvents and one or more alkali metal salts. (b) Add the aliphatic polycarbonate resin in two or more separate additions.

[0054] The above (b) includes at least the following (b1) and (b2): (b1) Add aliphatic polycarbonate resins (first time) (b2) After (b1), add aliphatic polycarbonate resins (second time). The above (b2) is carried out after at least a portion of the aliphatic polycarbonate resins added in (b1) has dissolved. Furthermore, the dissolution of at least a portion of the aliphatic polycarbonate resins added in (b1) can be visually confirmed, or it can be determined by using a viscometer or the like, as the viscosity of the mixture increases immediately after (b1).

[0055] When adding aliphatic polycarbonate resins in two or more portions, from the viewpoint of efficiently promoting the decomposition reaction by dissolving the aliphatic polycarbonate resins, the amount of aliphatic polycarbonate resin added per portion is preferably 0.10 parts by mass or less, more preferably 0.08 parts by mass or less, even more preferably 0.05 parts by mass or less, and even smaller amounts may be added, per 1.0 part by mass of the mixture of the organic solvent, water, and alkali metal salt. Similarly, from the same viewpoint, the time interval between adding the aliphatic polycarbonate resins is preferably 0.1 hours or more, more preferably 0.3 hours or more, even more preferably 0.5 hours or more, and even longer intervals may be used.

[0056] The method of (b) described above involves adding the aliphatic polycarbonate resins in two or more separate steps, and the number of steps is not limited to one. For example, the aliphatic polycarbonate resins may be added in stages in multiple steps. Expressing (b) from another perspective, in (b2), the aliphatic polycarbonate resins may be added in accordance with the rate at which the aliphatic polycarbonate resins added in (b1) dissolve. In this case, the aliphatic polycarbonate resins may be added in stages or continuously while dissolving the aliphatic polycarbonate resins.

[0057] By using this method, the decomposition products of the aliphatic polycarbonate resin dissolve in organic solvents or water, and fusion between resins is less likely to occur. Compared to adding the entire amount of resin at once, the deterioration of dispersibility and fluidity due to undissolved resin is suppressed, creating conditions that facilitate the decomposition reaction. In other words, by adding aliphatic polycarbonate resins little by little to decompose the resin and then dissolve it sequentially in the solvent, the decomposition reaction can be efficiently promoted.

[0058] Furthermore, "at least a portion of aliphatic polycarbonate resins" means "at least a portion of aliphatic polycarbonate resin and / or a composition containing said aliphatic polycarbonate resin." If only aliphatic polycarbonate resin is used, it means at least a portion of the aliphatic polycarbonate resin. If only a composition containing said aliphatic polycarbonate resin is used, it means a portion of the composition containing said aliphatic polycarbonate resin. If both aliphatic polycarbonate resin and a composition containing said aliphatic polycarbonate resin are used, it means at least a portion of the aliphatic polycarbonate resin and a composition containing said aliphatic polycarbonate resin.

[0059] The above (b1) may be carried out simultaneously with the above (a), or before or after the above (a). For example, the decomposition step may be carried out by adding water, one or more organic solvents, one or more alkali metal salts, and a portion of the aliphatic polycarbonate resins to a reaction vessel, mixing, and then adding the aliphatic polycarbonate resins at least once more; or by adding water, one or more organic solvents, and one or more alkali metal salts to a reaction vessel, mixing, and then adding the aliphatic polycarbonate resins in at least two portions.

[0060] Furthermore, in (a) above, the mixing order of water, one or more organic solvents, and one or more alkali metal salts is not particularly limited.

[0061] The aforementioned disassembly step may include (c) below. (c) Adjust the temperature of the mixture containing water, one or more organic solvents, and one or more alkali metal salts to 50°C or higher and 200°C or lower.

[0062] The above (c) can be performed at any time during the decomposition process. For example, (a) and (c) may be performed simultaneously, or (c) may be performed after (a). For example, if the reaction temperature is temperature Tt, the mixture may be heated after mixing water, an organic solvent, and an alkali metal salt, or the mixture may be heated while mixing water, an organic solvent, and an alkali metal salt, to adjust the mixture to temperature Tt.

[0063] Furthermore, the order of (b) and (c) is not particularly limited. (c) may be performed before (b1), (c) may be performed simultaneously with (b1) or (b2), (c) may be performed after (b1) and then (b2), or (c) may be performed after (b2).

[0064] When (c) is performed after (a), (a) is preferably performed at 10°C or higher, and more preferably at 20°C or higher. This is preferable because the mixing temperature is above the lower limit, which helps prevent solidification, poor mixing, etc.

[0065] In (c) above, the temperature of the mixture is adjusted to a reaction temperature set within the range of 50 to 200°C. The temperature of the mixture is the internal temperature of the mixture and can be controlled, for example, by the temperature of a thermometer installed in the adjustment tank (reaction tank) in which the mixture is prepared. Adjusting to a reaction temperature of 50 to 200°C means that the temperature of the thermometer in the adjustment tank becomes the reaction temperature. The reaction temperature is appropriately selected depending on the type of organic solvent and reaction time, but is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 75°C or higher, even more preferably 80°C or higher, and also preferably 120°C or lower, more preferably 110°C or lower, even more preferably 100°C or lower, and particularly preferably 95°C or lower. A reaction temperature below the above upper limit makes it easier to suppress the evaporation of water in the mixture necessary for hydrolysis, and depending on the melting point of the organic solvent, a temperature above the above lower limit tends to suppress the solidification of the organic solvent (for example, solidification of aromatic monoalcohols) and allow solvolysis to proceed appropriately.

[0066] Aliphatic polycarbonate resins may be partially mixed before temperature adjustment of the mixture, and the remainder added after temperature adjustment. In this case, the mixture adjusted to the reaction temperature contains water, one or more organic solvents, one or more alkali metal salts, and a portion of the aliphatic polycarbonate resins. Alternatively, the entire amount of aliphatic polycarbonate resins may be added after adjusting the temperature of the mixture. In this case, the mixture adjusted to the reaction temperature contains water, one or more organic solvents, and one or more alkali metal salts. To carry out the decomposition reaction more efficiently, it is preferable to add 50% by mass or more of the aliphatic polycarbonate resins used after adjusting the temperature of the mixture, more preferably 90% by mass or more, and even more preferably add the entire amount of aliphatic polycarbonate resins used after adjusting the temperature of the mixture.

[0067] In order to allow the decomposition reaction of aliphatic polycarbonate resins to proceed, it is preferable to stir the reaction system for a predetermined time after (b) above. Here, the reaction system refers to a mixture of the water, one or more organic solvents, one or more alkali metal salts, and the total amount of aliphatic polycarbonate resins.

[0068] The temperature within the reaction system is set between 50 and 200°C. The reaction temperature may be kept constant or varied over time.

[0069] The decomposition reaction in the reaction system may be carried out under atmospheric pressure or under pressurized pressure, but since the reaction proceeds sufficiently even under atmospheric pressure, it is preferable to carry it out under atmospheric pressure. In particular, the decomposition of aliphatic polycarbonate resins is preferably carried out at a reaction temperature of 60 to 120°C and atmospheric pressure, more preferably at a reaction temperature of 70 to 110°C and atmospheric pressure, and even more preferably at a reaction temperature of 80 to 100°C and atmospheric pressure.

[0070] The reaction time is appropriately selected depending on the amount of undissolved resin at the time the entire amount of aliphatic polycarbonate resin has been added, the reaction temperature, etc. However, from the viewpoint of suppressing the decomposition of decomposition products such as the generated monomers, the reaction time in the reaction system is preferably 30 hours or less, and is more preferably shorter in the order of 25 hours or less, 20 hours or less, 15 hours or less, 10 hours or less, and 5 hours or less. Furthermore, from the viewpoint of allowing the decomposition reaction to proceed sufficiently, the reaction time in the reaction system is preferably 0.1 hours or more, more preferably 0.5 hours or more, and even more preferably 1 hour or more.

[0071] The reaction time in the reaction system is defined as the time from when the entire amount of aliphatic polycarbonate resin has been added until the start of operations to stop the decomposition reaction (such as neutralization or removal of organic solvents). The endpoint of the reaction time in the reaction system may also be determined by tracking the decomposition reaction using gas chromatography or liquid chromatography.

[0072] (neutralization) The decomposition method of the present invention preferably includes a neutralization step in which an acid is added to the reaction system after the decomposition step to neutralize it.

[0073] Acids used for neutralization include hydrochloric acid, sulfuric acid, and phosphoric acid. In the neutralization process, the pH of the reaction system at the end of neutralization is preferably 6.0 to 10.0, more preferably 6.5 or higher, even more preferably 7.0 or higher, more preferably 9.5 or lower, and even more preferably 9.0 or lower. A pH of the reaction system at the end of neutralization above the lower limit tends to prevent corrosion of the reaction vessel and maintain the quality of the isolated monomer, while a pH below the upper limit tends to suppress the hydrolysis of the monomer and maintain the monomer yield.

[0074] During the decomposition process, carbonates are produced when the carbonate bonds of aliphatic polycarbonate resins react with water. These carbonates react with an acid during neutralization to produce carbon dioxide. In the decomposition method of the present invention, this carbon dioxide may be recovered and purified.

[0075] (Removal of solid foreign matter) Furthermore, it is preferable to perform a filtration step to remove solid foreign matter after the neutralization step.

[0076] (Removal of organic solvents and water) The decomposition method of the present invention preferably includes a removal step after the decomposition step, in which the organic solvent and water in the reaction system are removed by reduced-pressure distillation.

[0077] (Monomer recovery) Aliphatic alcohols having two or more hydroxyl groups, which are monomers produced by decomposing aliphatic polycarbonate resins, are readily soluble in water and difficult to extract and wash with organic solvents such as aromatic solvents. Therefore, it is preferable to remove solid impurities by filtration, remove light-boiling components by reduced-pressure distillation, and then recover the monomers by distillation or crystallization.

[0078] The decomposition method of the present invention preferably comprises a removal step of removing organic solvents and water from the reaction system by vacuum distillation after a filtration step, and a monomer recovery step of distilling the solids produced by vacuum distillation in the removal step under high vacuum to obtain an aliphatic alcohol having two or more hydroxyl groups, which is a monomer. Specifically, an acid is added to the reaction system to neutralize it, and after filtration, the reaction system is depressurized using a distillation apparatus to distill off the organic solvent and water, leaving a solid residue inside the apparatus. Since this solid residue contains monomers, the monomers (i.e., aliphatic alcohols having two or more hydroxyl groups) can be further recovered by distillation under high vacuum.

[0079] Furthermore, the decomposition method of the present invention preferably comprises a removal step of removing the organic solvent and water in the reaction system by vacuum distillation after the filtration step, a step of removing insoluble matter (for example, the alkali metal salt and the salt derived from the acid added in the neutralization step) by dissolving the solids produced by vacuum distillation in the removal step in alcohol and filtering, and a step of crystallizing and recovering the aliphatic alcohol having two or more hydroxyl groups, which is the monomer.

[0080] (high purity) To obtain aliphatic alcohols (monomers) having two or more hydroxyl groups of higher purity, the decomposition method of the present invention preferably includes a purification step of further purifying the aliphatic alcohols having two or more hydroxyl groups, recovered by distillation or crystallization, by one or more of the following: crystallization, filtration, or distillation.

[0081] The decomposition method of the present invention is preferably, as an example, a method comprising the following (1) to (5). (1) A process of decomposing aliphatic polycarbonate resins in the presence of water, one or more organic solvents, and one or more alkali metal salts. (2) A step in which an acid is added to the reaction system after decomposition to neutralize it. (3) A step of filtering the reaction solution after (2) through a filter to remove solid foreign matter. (4) The reaction solution after (3) above is removed by distillation under reduced pressure to remove light boiling components including organic solvents and water from the reaction system. (5) A step of distilling the solids produced by the vacuum distillation in (4) above under high temperature and high vacuum to distill off a monomer, an aliphatic alcohol having two or more hydroxyl groups, and recovering the monomer.

[0082] As another example, the decomposition method of the present invention is preferably a method having the following (1) to (4), (5a), (6) and (7). (1) A process of decomposing aliphatic polycarbonate resins in the presence of water, one or more organic solvents, and one or more alkali metal salts. (2) A step in which an acid is added to the reaction system after decomposition to neutralize it. (3) A step of filtering the reaction solution after (2) through a filter to remove solid foreign matter. (4) The reaction solution after (3) above is removed by distillation under reduced pressure to remove light boiling components including organic solvents and water from the reaction system. (5a) A step in which the solids produced by the vacuum distillation in (4) above are dissolved or dispersed in alcohol, and then filtered to remove any undissolved salts. (6) A step of crystallizing (cooling) the liquid after (5a) and recovering the precipitated monomer, which is an aliphatic alcohol having two or more hydroxyl groups. (7) A step of distilling the monomer recovered in (6) under high temperature and high vacuum and recovering the distilled monomer.

[0083] Thus, the solvent adhering to the monomer recovered in (6) can be removed by reduced-pressure distillation. High-purity monomers can be obtained by performing (7) after (6).

[0084] Furthermore, the organic solvent removed in the step of removing the light boiling component in (3) above can be recycled as the organic solvent in (1) above.

[0085] The decomposition products obtained by the decomposition method of the present invention include monomers that constitute the aliphatic polycarbonate resin, which is the raw material. Therefore, the present invention can also be a method for producing monomers that constitute the aliphatic polycarbonate resin, which includes the decomposition method of the present invention.

[0086] <Uses of monomers> The monomers obtained by the decomposition method of the present invention (hereinafter sometimes referred to as "recycled monomers") can be used as biomass raw materials for polycarbonate resins, polyester resins, polyurethane resins, etc. They can also be used in medical pharmaceuticals such as diuretics and Meniere's disease treatment agents.

[0087] An example of a method using recycled monomers as raw materials is a production method comprising the steps of obtaining an aliphatic alcohol having two or more hydroxyl groups by the decomposition method of the present invention, and obtaining a polymer and / or a composition containing the polymer using the obtained aliphatic alcohol. This makes it possible to obtain a polymer having constituent units derived from aliphatic alcohol and a composition containing the polymer. For example, an aliphatic polycarbonate resin can be obtained by polycondensing an aliphatic alcohol obtained by the decomposition method of the present invention with a diester carbonate.

[0088] Furthermore, an aliphatic alcohol derivative can be obtained by a production method comprising the steps of obtaining an aliphatic alcohol having two or more hydroxyl groups by the decomposition method of the present invention, and obtaining an aliphatic alcohol derivative using the obtained aliphatic alcohol.

[0089] Thus, when producing polymers or derivatives using recycled monomers as raw materials, recycled monomers may be used alone or in combination with unused monomers. The method for obtaining polymers or derivatives can be the same as the method used when unused monomers are used. [Examples]

[0090] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0091] [Aliphatic polycarbonate resin] As the raw material, an aliphatic polycarbonate resin was used that contained repeating units (A-1) containing isosorbide (ISB)-derived structural units represented by the above general formula (1p) and repeating units (A-3) containing 1,4-cyclohexanedimethanol (CHDM)-derived structural units represented by the above general formula (2p).

[0092] The composition ratio (NMR) and average molecular weight of the repeating units of the aliphatic polycarbonate resin were determined as follows. Approximately 15 mg of the aliphatic polycarbonate resin sample used as a raw material was weighed out and dissolved in approximately 0.7 mL of deuterated chloroform. This solution was placed in an NMR tube with an inner diameter of 5 mm, and the 1H-NMR spectrum was measured under the following conditions. The molar ratio of each repeating unit in the aliphatic polycarbonate resin was calculated based on the integral ratio (area ratio) of the signals of repeating unit (A-1) and repeating unit (A-3), and the number of protons in each signal. • Device: JNM-ECZ400S (manufactured by JEOL Ltd.) ·Measurement temperature: 30℃ • Relaxation time: 6 seconds • Total number of times: 64

[0093] Furthermore, the average molecular weight of each repeating unit was calculated using the following formula, based on the proportion of each repeating unit when the sum of the molar ratios of repeating units (A-1) and (A-3) is set to 100%. Molecular weight of repeating unit (A-1) × Percentage of repeating unit (A-1) (mol%) + Molecular weight of repeating unit (A-3) × Percentage of repeating unit (A-3) (mol%) = Average molecular weight of repeating units

[0094] The above measurements revealed that the aliphatic polycarbonate resin used as the raw material was a copolymer with repeating units (A-1): (A-3) = 70:30 (mol%), and the average molecular weight of the repeating units was 171.56.

[0095] [Quantitative determination of obtained monomers] The quantitative analysis of isosorbide (ISB) and 1,4-cyclohexanedimethanol (CHDM) in the reaction solution was performed using an Agilent Technologies GC-8860 (FID detector) under the following measurement conditions, based on calibration curves prepared using ISB and CHDM standards. • Column: DB-1 (inner diameter 0.25 mm, length 30 m, film thickness 0.25 μm) ·Injection volume: 1μL • Injection method: Split ratio 50:1 ·Inlet temperature: 250℃ Detector temperature: 320℃ Oven: 50°C (2 minutes) → 10°C / minute → 150°C → 15°C / minute → 300°C (5 minutes)

[0096] [Example 1] Under a nitrogen atmosphere, 25 g of 1-butanol (BuOH), 7.77 g of 30% NaOH aqueous solution, and 10.3 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 100°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 100°C for 5 hours. GC analysis of the reaction solution showed monomer yields of 97% ISB and 99% CHDM.

[0097] [Example 2] Under a nitrogen atmosphere, 25 g of BuOH, 11.66 g of 30% NaOH aqueous solution, and 7.58 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 100°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 100°C for 3 hours. GC analysis of the reaction solution showed monomer yields of ISB 96% and CHDM 94%.

[0098] [Example 3] Under a nitrogen atmosphere, 25 g of BuOH, 11.66 g of 30% NaOH aqueous solution, and 7.58 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 3 hours. GC analysis of the reaction solution showed monomer yields of 86% ISB and 85% CHDM.

[0099] [Example 4] Under a nitrogen atmosphere, 25 g of BuOH, 11.66 g of 30% NaOH aqueous solution, and 2.33 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 5 hours. GC analysis of the reaction solution showed monomer yields of ISB 73% and CHDM 88%.

[0100] [Example 5] Under a nitrogen atmosphere, 25 g of isopropyl alcohol (IPA), 11.66 g of 30% NaOH aqueous solution, and 7.58 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 80°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 80°C for 5 hours. GC analysis of the reaction solution showed monomer yields of 83% ISB and 92% CHDM.

[0101] [Example 6] Under a nitrogen atmosphere, 20 g of 4-methyltetrahydropyran (MTHP), 7.77 g of 30% NaOH aqueous solution, 5.94 g of water, and 0.09 g of tetrabutylammonium bromide (TBAB) were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 5 hours. GC analysis of the reaction solution showed monomer yields of 81% ISB and 83% CHDM.

[0102] [Example 7] Under a nitrogen atmosphere, 25 g of MTHP, 11.66 g of 30% NaOH aqueous solution, 7.58 g of water, and 0.09 g of TBAB were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour and the mixture was reacted at 90°C for 3 hours. GC analysis of the reaction solution showed monomer yields of ISB 88% and CHDM 86%.

[0103] [Example 8] Under a nitrogen atmosphere, 25 g of MTHP, 7.77 g of 30% NaOH aqueous solution, 5.05 g of water, and 0.09 g of TBAB were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 100°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 100°C for 5 hours. GC analysis of the reaction solution showed monomer yields of 83% ISB and 70% CHDM.

[0104] [Example 9] Under a nitrogen atmosphere, 25 g of MTHP, 11.66 g of 30% NaOH aqueous solution, 7.58 g of water, and 0.09 g of TBAB were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 100°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 100°C for 5 hours. GC analysis of the reaction solution showed monomer yields of 88% ISB and 93% CHDM.

[0105] [Example 10] Under a nitrogen atmosphere, 25 g of MTHP, 15.54 g of 30% NaOH aqueous solution, 10.1 g of water, and 0.09 g of TBAB were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 100°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 100°C for 5 hours. GC analysis of the reaction solution showed monomer yields of 99% ISB and 99% CHDM.

[0106] [Example 11] Under a nitrogen atmosphere, 25 g of phenol (PHL), 3.89 g of 30% NaOH aqueous solution, and 2.95 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 15 hours. GC analysis of the reaction solution showed monomer yields of ISB 97% and CHDM 71%.

[0107] [Example 12] Under a nitrogen atmosphere, 25 g of PHL, 7.77 g of 30% NaOH aqueous solution, and 5.94 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 15 hours. GC analysis of the reaction solution showed monomer yields of ISB 96% and CHDM 74%.

[0108] [Example 13] Under a nitrogen atmosphere, 25 g of PHL, 11.66 g of 30% NaOH aqueous solution, and 7.58 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 8 hours. GC analysis of the reaction solution showed monomer yields of ISB 96% and CHDM 76%.

[0109] [Example 14] Under a nitrogen atmosphere, 25g of PHL, 6.81g of 48% KOH aqueous solution, and 7.42g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 10 hours. GC analysis of the reaction solution showed monomer yields of ISB 94% and CHDM 73%.

[0110] [Example 15] Under a nitrogen atmosphere, 25g of PHL, 3.41g of 48% KOH aqueous solution, and 3.68g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 100°C, 5g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 100°C for 10 hours. GC analysis of the reaction solution showed monomer yields of ISB 99% and CHDM 84%.

[0111] [Example 16] Under a nitrogen atmosphere, 25 g of PHL, 6.81 g of 48% KOH aqueous solution, and 7.42 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 100°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 100°C for 7 hours. GC analysis of the reaction solution showed monomer yields of 99% ISB and 85% CHDM.

[0112] [Example 17] Under a nitrogen atmosphere, 25.5 g of PHL, 1.94 g of 30% NaOH aqueous solution, and 1.47 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 90°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour and the reaction was carried out at 90°C for 15 hours. GC analysis of the reaction solution showed monomer yields of 40% ISB and 38% CHDM.

[0113] [Example 18] Under a nitrogen atmosphere, 25 g of o-xylene (o-Xy), 7.77 g of 30% NaOH aqueous solution, 5.05 g of water, and 0.09 g of TBAB were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. The temperature was then raised to 100°C, and 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, while the reaction was carried out at 100°C for 8 hours. GC analysis of the reaction solution showed monomer yields of 60% ISB and 40% CHDM.

[0114] [Example 19] Under a nitrogen atmosphere, 20 g of toluene (TL), 7.77 g of 30% NaOH aqueous solution, 5.94 g of water, and 0.09 g of TBAB were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. The temperature was then raised to 90°C, and 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 90°C for 10 hours. GC analysis of the reaction solution showed monomer yields of ISB 66% and CHDM 50%.

[0115] [Comparative Example 1] Under a nitrogen atmosphere, 25g of BuOH, 7.77g of 30% NaOH aqueous solution, 10.3g of water, and 5g of aliphatic polycarbonate resin were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. When the temperature was raised to 100°C, the resin formed clumps and stirring stopped, so the reaction was interrupted.

[0116] [Comparative Example 2] Under a nitrogen atmosphere, 25 g of BuOH, 14.75 g of triethylamine (TEA), and 3.15 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 85°C, 5 g of aliphatic polycarbonate resin was added in small increments over 1 hour, and the reaction was carried out at 85°C for 8 hours. GC analysis of the reaction solution showed no decomposition of ISB or CHDM (yield 0%).

[0117] [Comparative Example 3] Under a nitrogen atmosphere, 20 g of PHL, 2.95 g of triethylamine (TEA), and 2.62 g of water were added to a flask equipped with a stirrer, condenser, and thermometer at room temperature and stirred. After raising the temperature to 75°C, 5 g of aliphatic polycarbonate resin was added in small amounts over 1 hour, and the reaction was carried out at 75°C for 15 hours. GC analysis of the reaction solution showed monomer yields of 11% ISB and 10% CHDM.

[0118] Table 1 shows the results for Examples 1 to 19, and Table 2 shows the results for Comparative Examples 1 to 3. As shown in Comparative Example 1, when the entire amount of aliphatic polycarbonate resin was added at once, stirring became impossible, and monomers could not be obtained. Furthermore, compared to Comparative Examples 2 and 3, which used triethylamine as a catalyst, Examples 1 to 19 were able to obtain monomers in a higher yield.

[0119] [Table 1]

[0120] [Table 2]

Claims

1. A method for decomposing a polycarbonate resin and / or a composition containing said polycarbonate resin, The process includes a decomposition step of decomposing the polycarbonate resin and / or the composition in the presence of water, one or more organic solvents and one or more alkali metal salts, The polycarbonate resin is a resin having structural units derived from aliphatic alcohols having two or more hydroxyl groups and carbonate bonds. A method for decomposing a polycarbonate resin and / or a composition containing the polycarbonate resin, wherein in the decomposition step, the polycarbonate resin and / or the composition is added in two or more portions, and the step of adding the polycarbonate resin and / or the composition a second time is performed after at least a portion of the polycarbonate resin and / or the composition added the first time has dissolved.

2. The method according to claim 1, wherein the decomposition step includes adding the polycarbonate resin and / or a composition containing the polycarbonate resin to a mixture containing the water, the organic solvent, and the alkali metal salt, which has been adjusted to a temperature of 50°C or higher and 200°C or lower.

3. The method according to claim 1, wherein the one or more organic solvents include polar organic solvents.

4. The method according to claim 1, wherein the one or more alkali metal salts include a metal hydroxide.

5. The method according to claim 1, wherein the amount of water is 6.0 moles or more and 100.0 moles or less per 1.0 mole of repeating units of the polycarbonate resin in the composition.

6. The method according to claim 1, wherein the amount of one or more alkali metal salts is 0.6 moles or more and 20.0 moles or less per 1.0 mole of repeating units of the polycarbonate resin in the polycarbonate resin and / or the composition.

7. A decomposition step of decomposing the polycarbonate resin and / or the composition to obtain decomposition products, After the aforementioned decomposition step, a neutralization step is performed in which an acid is added to neutralize the substance. The method according to claim 1, further comprising a filtration step to remove solid foreign matter after the neutralization step.

8. Furthermore, a removal step is performed by vacuum distillation to remove the organic solvent and water, The method according to claim 7, further comprising a monomer recovery step of distilling the solids generated by the reduced-pressure distillation in the removal step under high vacuum to obtain a monomer, which is an aliphatic alcohol having two or more hydroxyl groups.

9. Furthermore, a removal step is performed by vacuum distillation to remove the organic solvent and water, The process involves removing insoluble matter by dissolving the solids generated during the vacuum distillation in the aforementioned removal process in alcohol and filtering it, The method according to claim 7, comprising the step of crystallizing and recovering the monomer, which is an aliphatic alcohol having two or more hydroxyl groups.

10. The method according to claim 8 or 9, further comprising a purification step of purifying the obtained aliphatic alcohol by one or more of the following: crystallization, filtration, or distillation.

11. The method according to claim 1, wherein the aliphatic alcohol containing two or more hydroxyl groups includes an aliphatic alcohol represented by the following formula (1m). 【Chemistry 1】

12. The method according to claim 11, wherein the polycarbonate resin contains structural units derived from a dihydroxy compound different from the dihydroxy compound represented by formula (1m).

13. The method according to claim 1, wherein the aliphatic alcohol containing two or more hydroxyl groups comprises 1,4-cyclohexanedimethanol.

14. A method for producing monomers constituting the polycarbonate resin, comprising the method according to claim 1.

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